resizeImg.js

angular.module('myModule')
	.directive('resizeImg', function() {
	    return {
	    	restrict: 'A',
	    	link: function(scope, element, attrs) {
	      		       
	      		var width = element.parent().width();
	      		var maxHeight = attrs.height;
		        var newHeight, newWidth;
	 
		        var img = new Image();
		       
		        
		        img.onload = function() { 
		            if( (width / this.width ) > (maxHeight / this.height) ) {
		            	newWidth = maxWidth;
		              	newHeight = Math.round( (width * this.height) / this.width);
		            } else {
		              	newHeight = maxHeight;
		              	newWidth = Math.round( (maxHeight * this.width) / this.height);
		            }

		            element.parent().css({
		               'background-image': 'url(' + attrs.ngSrc + ')',
		               'background-size': newWidth + 'px ' + newHeight + 'px',
		               'width': '100%',
		               'height': maxHeight + 'px',
		               'display': 'block',
		               'background-position': 'center center',
		               'background-repeat': 'no-repeat'
		            });
		            element.css('display', 'none');
	 
		        };
	 
		        img.src = attrs.ngSrc;
	    	}
	    }
 
});